Alternative methods to attach components in printed circuit boards
to improve their recyclability
André Canal-Marques a, Maria Rita Ortega-Vega b, José-María Cabrera c & Célia de Fraga-Malfatti d
a
Departamento de Metalurgia (DEMET)/PPGE3M, Universidade Federal do Rio Grande do Sul, Brazil, [email protected]
Departamento de Metalurgia (DEMET)/PPGE3M, Universidade Federal do Rio Grande do Sul, Brazil, [email protected]
c
Universitat Politécnica de Catalunya, ETSEIB, Barcelona, Spain – Fundació CTM Centre Tecnológic, Materials Forming Area, Manresa, Spain,
[email protected]
d
Departamento de Metalurgia (DEMET)/PPGE3M, Universidade Federal do Rio Grande do Sul, Brazil, [email protected]
b
Received: September 3th, de 2013. Received in revised form: March 19th, 2014. Accepted: July 22th, 2014
Abstract
Printed circuit boards (PCB), which form the basis of the electronics industry, generate wastes that are difficult to dispose of and recycle
due to the diversity of their materials and components and their difficult separation. The replacement of Pb-Sn welding for lead-free
alloys to attach components in printed circuit boards is an attempt to minimize the problem of Pb toxicity, but it does not change the
problem of separation of the components for later reuse and/or recycling. This article presents a review of the environmental problem of
printed circuit boards, the initial development of alternative fixation studies, and reliability tests for comparison with conventional boards
and commercial systems to validate or serve as a basis for future research, focused on PCB disassembly for recycling. At present, initial
studies were performed by using prototypes for visual and functional tests.
Keywords: Printed circuit boards, Welding replacement, Environmental problem, Recyclability.
Métodos alternativos de fijación de componentes de circuitos
impresos para mejorar su reciclabilidad
Resumen
Las Placas de Circuitos Impresos constituyen la base de la industria electrónica. Sin embargo, generan residuos de difícil eliminación y
reciclaje, debido a la diversidad de materiales y componentes presentes y su difícil separación. La sustitución de soldaduras de Pb-Sn por
aleaciones libres de plomo intenta minimizar la toxicidad que implica la presencia de Pb, pero no aborda la separación de los
componentes para su posterior reutilización y/o reciclaje. Este artículo presenta una revisión bibliográfica sobre el problema ambiental
que constituyen las placas de circuitos impresos, el estudio de alternativas de fijación, pruebas de fiabilidad para comparar con las placas
convencionales y sistemas comerciales para validar o servir de base para futuras investigaciones, enfocadas hacia el desmontaje de PCI.
Además, se muestran algunos estudios incipientes mediante prototipos para la realización de pruebas visuales y funcionales.
Palabras clave: Placas de circuitos impresos, Reemplazo de soldadura, Problema ambiental, Reciclabilidad
1. Introduction
Currently, there are a large number of products that
generate waste and significantly increase the volume of dumps
and landfills due to innovation by the electronic industry.
Much of the waste generated constitutes technological waste,
whose recycling is being studied by several authors, due to its
social and environmental relevance. Among these wastes, one
of the most important are printed circuit boards (PCBs), which
are the base of the electronic industry.
PCBs constitute a kind of waste with difficult disposal
because their recycling is complex and expensive. The
diversity of materials and components present in them
make their separation difficult. Separation of electronic
components and reusing of these materials require the
removal of the solder, which is a complex process. Also
and for the majority of cases, such components are
unusable after that process due to the temperatures
involved.
The PCBs construction process is currently migrating
from traditional eutectic Pb-Sn alloy to different lead-free
alloys. This replacement attempts to alleviate the problem
© The authors; licensee Universidad Nacional de Colombia.
DYNA 81 (186), pp. 146-152. August, 2014 Medellín. ISSN 0012-7353 Printed, ISSN 2346-2183 Online
Canal-Marques et al / DYNA 81 (186), pp. 146-152. August, 2014.
Figure 1. A) Remainders of acid-treated circuit boards and processing waste
along the Lianjiang River, China. B) Recovery of gold from PCB wastes using
acid baths.
Source: Ban [10].
of Pb-Sn solder alloy, considered toxic, but does not change
the component separation problem for reuse and/or recycling.
Therefore, alternatives to the removal and disposal of these
materials without harming the environment become a new
challenge.
The discarded PCBs have attracted public and researchers
attention [1-9], since among their components there are toxic
materials such as heavy metals and brominated flame
retardants (BFRs), causing enormous damage to the
environment if they are not properly treated (Fig. 1).
In general, PCB waste components can be divided into
metallic (MFs) and non-metallic fractions (NMF) [11]. NMF
typical composition comprises thermosetting resins (epoxy),
glass fiber, plastics, reinforcement materials, additives and
other BFR, and constitute about 70wt-% of the PCB wastes.
Thermosetting resins cannot be recast or remodeled because of
their molecular structure and not recyclable [11]. The
proportion of waste printed circuit boards WPCBs in
electronics waste is approximately 3% [12,13].
Several authors [1, 14-21], argue that WPCBs plastics
contain BFR, including polybrominated biphenyls (PBBs) and
polybrominated diphenyl ethers (PBDEs). Their combustion
generates highly toxic gases, called polybrominated
dibenzodioxins and dibenzofurans, and dioxins and furans
(PCDF/Fs) and glass fiber significantly reduces fuel
efficiency. Traditionally, these nonmetallic materials are
landfilled or incinerated resulting in wasted resources and
aggravating the environmental problem [5, 22-26].
The metal fraction is comprised of ~16% of copper, ~4%
of tin-lead, ~3% of iron, ~2% of nickel, ~0.05% of silver,
~0.03% of gold, ~0.01% palladium [14,17, 27-30] and even
rare elements such as tantalum, covered or mixed with various
plastics and ceramics [31]. Li [32] states that the purity of the
precious metals in PCBs is 10 times higher than minerals rich
in these elements. Cui and Zhang [33] argue that the main
economic objective for e-waste recycling is the recovery of
precious metals.
It is usually difficult and often confusing to quantify the
environmental consequences associated with materials,
processes and products. The difficulties are, for example, the
determination of the environmental effects associated with the
objects of the comparison, the almost impossible task of
comparing different environmental effects and the amount of
data needed to compare related products. Sometimes, the
necessary data are also scarce or inaccessible, and then it is
difficult to define the environmental load analysis.
Furthermore, the electronic industry is extremely large and
147
varied, characterized by long supply chains, and in the
same way, indirect environmental impacts associated to
their products [34].
There is a strong pressure from European companies
not to accept most electronic products with a tin-lead
solder printed circuit board, due to its toxicity. This type
of welding is used, because of its easy installation and
use, but, since European laws became highly restrictive
for this type of material, it is important to study other
types of welding, which are less aggressive to the
environment [35].
Jie [36] argues that there is a growing environmental
awareness around the world. Therefore, an economically
viable environmental management system for the electroelectronic equipment end of life cycle is necessary. It is
very important for sustainable development, as the
effective cost and efficient environmental methods are
needed to manage these wastes [29-30, 37-40].
According to Andrae [34] and other authors [41-43], a
number of methods and tools related to environmental
assessment, such as life cycle assessment (LCA) and
carbon footprint, were proposed in order to indicate
which alternative is better compared to others.
Schematically, the life cycle of a product consists of four
stages: material extraction and processing, manufacture,
usage and end of life.
Griese et al. [44] argues that studies confirmed that
lead is the material with the greatest potential to be
removed and had to be banned to prevent uncontrolled
releases; also, Pb-free alloys reduce the potential
environmental impact of electronics. This requires a
complete LCA and detailed study of the environmental
performance of new materials substituents.
Some authors [45-48] realized that there is no simple
replacement for traditional welding. They indicate that
the introduction of lead-free solders reduces toxicity and
potential risks in the electric-electronic waste removal.
But lead-free solders are less efficient in terms of
resource and energy consumption. Compared with
traditional Sn-Pb solder, Pb-free materials manufacturing
doubles the cost in industries, increases energy use and
promotes the loss of valuable resources. In fact, Turbini
et al. [49] recommend increasing the conventional Pbbased electronics recycling, instead of introducing leadfree solder. The main reason is to recycle copper in order
to reduce the environmental problems associated with its
primary production and mineral extraction.
Several studies are underway to reduce or completely
eliminate welding in printed circuit board manufacture.
These alternatives provide initial solutions to the
problem, by reducing the use of soldering or replacing the
welding by another fastener such as a resin. However,
they do not solve the problem of separation. The ways in
which electronic components are fixed in PCBs still lacks
adequate solutions. Therefore, fixing mechanisms used on
a printed circuit board are considered an open research
topic.
Thus, this work reconsiders the alternatives for fixing
the components on printed circuit boards, through
studying the supports used in printed circuit boards, the
Canal-Marques et al / DYNA 81 (186), pp. 146-152. August, 2014.
existing types, properties and processes, seeking to explore
alternatives to traditional fixing (welding) in a printed circuit
board. Prototypes are made by mounting a board from
established concepts and making comparative tests of
reliability, compared to conventionally fixed boards for
validation and providing a basis for future research.
The aim is to develop new alternatives and designs to
improve the fastening through alternative systems that
facilitate assembly, disassembly and maintenance of various
components of the product during the separation process, prior
to recycling. Until now, there have been some initial studies
using prototypes for testing, including visual and functional
testing.
2. Materials and methods
2.1. Study of two boards: Materials analysis
The present analysis was performed for two printed circuit
boards regarding the percentage of each material, in order to
evaluate the recycling viability. This study was conducted
with the cooperation of a PCBs manufacturing company,
located in the town of Valls (Tarragona-Barcelona) in Spain,
which provided the boards and the initial data (Fig. 2).
2.2. Fixing of components by pressure
This work has applied for a patent with the INPI (National
Institute of Industrial Property of Brazil), with the name
Production Process of Printed Circuit Boards and the
Resulting Product on 07/03/2013, number (BR 10 2013
005511 5).
The purpose of this study was to develop new methods for
attaching electronic components on a printed circuit board,
through alternative processes, and by selecting appropriate
materials for these processes, aiming to sustainability. Six
initial conceptual designs were analyzed. The criteria for the
analysis were: mechanical fixing, electronic connection
ability, electrical conductivity, ease of assembly/disassembly,
and low amount of material used. In the present study, the
component junctions were made by pressure. Boards were
fabricated to test the technical feasibility, analyzing its initial
run. The traditional process of manufacturing was maintained
Figure 2. PCB used.
Source: The authors.
with the addition of new steps after the traditional ones,
where a series of procedures was carried out to make a
board with fillets and holes adequate for mounting the
electronic circuit.
In this method of attachment, the board is made of
two parts, one with the printed circuit, which is pierced,
and whose elements are fixed by pressing on the other
board; this does not require welding. The contacts are
made internally so that circuit designs are not visible. The
elements junction is performed by the two boards placed
one on the other, pressing the device and connections,
and other items on the sides to further secure the
assembly.
For this set a simple circuit was designed (Fig. 3) to
be applied onto the board and the components to be fixed,
in order to test the proposal regarding the electrical
resistance at each point of the fixed contact elements, and
therefore test the initial conceptual model feasibility.
Virtual and physical prototypes were performed. The next
step was a functional prototype building. For this
prototype, a two-faced positive photosensitive board was
used, with dimensions of 100x160mm, made with
fiberglass epoxy resin (FR4), fire resistant insulation and
covered with a conductive copper thin film on both sides.
A circuit with components for SMD (Surface Mount
Device) and Through-hole were designed to test the two
types that are currently used. 10 resistances (5 SMD and
5 Through-hole), 10 Through-hole LEDs, 10 “chips” (5
SMD and 5 Through-hole) and a battery connected to the
system to verify operation were used. After the traditional
steps to create a PCB were carried out, a series of
procedures was performed leading to a track with the
same size of the board and the suitable holes for
mounting an electronic circuit.
In order to compare the proposed system with the
welding-fixed systems, three prototypes were fabricated
using the same method: The first prototype, with
junctions of tin-lead (60Sn-40Pb), the second one, leadfree welded (99.3 Sn-0.7Ag), and the third, with the
previously described junction method.
Figure 3. Schematic layout of the PCB.
Source: The authors.
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Canal-Marques et al / DYNA 81 (186), pp. 146-152. August, 2014.
2.3. Tests performed
At this stage, prototypes were submitted to reliability,
visual and operating tests.
2.3.1. Visual test
Figure 6. PCB prototype with union method developed. Source: Author.
Visual analysis was performed as the first characterization
of prototypes. A visual inspection of the board can help to
identify and troubleshoot contacts.
2.3.2. Performance test
The performance test consists of checking the correct
operation of the board, determining the integrity of all
electrical connections and checking all LED points, in order to
identify some damaged points and components within the
circuit in real working conditions.
2.3.3. Pending tests
The following tests will be carried out in the continuation
of this work: Test of corrosion and humidity electric
endurance test and thermal-mechanical fatigue.
3. Results and analysis
3.1. Study of two boards: Materials analysis
The percentage of each material in these two printed circuit
projects was calculated from data provided by the company. In
Table 1, the composition of the materials with greater presence
B - 238.37g
A – 383.70g
Table 1.
Comparison of PCBs regarding materials.
Materials
Board
Polyamide 6
Copper alloy
PA6 GF10+GB20
PBT+PET+ASA GF30
Magnetic iron
Steel alloy
Soldering paste “lead free” L F318
Total analyzed
Polymers
Metals
Composites
Ceramics
Total analyzed
E/P-I-GF20+MD10
Semi-components
PCB-Prepreg “adhesive”
Copper alloy
PBT
C2600 Brass
Soldering paste MP100 SN62
Total analyzed
Polymers
Metals
Composites
Ceramics
Total analyzed
Source: The authors.
Weight (g) Total percentage
144.05
37.54%
37.15
7.23%
25.96
6.77%
13.86
3.61%
10.82
2.82%
5.63
1.47%
4.80
1.25%
328.49g
85.61 %
219.07
57.09%
61.71
16.20%
46.07
11.89%
1.82
0.47%
328.49g
85.61 %
52.00
21.81%
38.50
16.15%
21.00
8.81%
19.92
8.36%
13.35
5.60%
6.30
2.64%
2.5
1.049%
184.02
77.2%
49.49
26.89%
80.27
43.62%
53.79
29.23%
0.46
0.25%
184.02g
77.2%
149
in the printed circuit board and a comparison between the
two boards studied, in relation to the percentage of the
materials, are shown.
There is a high weight percentage of polymeric
materials. Polyamide 6 is the material for the base of
board. Also, there is the presence of solder paste LF318
(Sn98.5/Ag1/Cu0.5) representing 1.25% of the total
weight of the printed circuit board. The main component
of the solder, Sn, is a metal component considered
moderately toxic. In the second board there is a high
weight percentage of composite materials over other
materials; the reinforced glass fiber is the base material
for the PCB
From Table 1, it can be seen that there is a great
difference in the amount of material used for the two
boards. Each board consists of a specific design for a
particular use, so its components change considerably.
This indicates how difficult the identification and
separation of the materials can be, as well as the
complexity of PCB recycling.
3.2. Fixing
The physical and virtual prototypes of the first tests
are shown in Fig.s 4, 5 and 6. The main objective of these
prototypes is to test the electrical resistance at each
contact point between the fixed elements and, therefore,
to test the feasibility of the initial concept.
Figure 4. Assembly components with folding rods through-hole
components. Source: Author.
Figure 5. PCB simulation on 3D software and assembly of the
prototype.
Source: The authors.
Canal-Marques et al / DYNA 81 (186), pp. 146-152. August, 2014.
Figure 7. PCB with the proposed circuit using SMD and Through-Hole.
Source: The authors.
From the first prototype, a new circuit design with LEDs
was used to test the performance of the attachment system.
Fig. 6 shows the virtual prototype and Fig. 7, the physical
prototype. This circuit design is more functional, simpler and
with higher quality.
In Fig. 8 the three prototypes appear in their respective
order, in order to compare different procedures and finishing
of the boards. The third prototype has the characteristic of not
using welding for component junctions, and hence facilitates
disassembly and reuse of components; this binding is nonpermanent.
Figure 9. Images of copper lines and connections made with pressure.
Source: The authors.
3.3.2. Performance test
In this test, we examined the operation of the system
through the operation check on all connection points with
the illumination of the "LEDs", shown in Fig. 10. Note
that the LEDs were lighted due to the pressure maintained
in the system. The identification of this problem will help
to improve other prototypes.
Figure 10. PCB operation.
Source: The authors.
Figure 8. PCBs prototypes with lead-tin solder and other lead-free.
Source: The authors.
3.3.3. Pending tests
3.3. Tests results
3.3.1. Visual test
In this test copper lines and connections between the track
and the components were visually checked, seeking out
possible errors. The result showed that the defects were not
detected visually in the system (Fig. 9).
150
Prototypes will be developed with better quality and
with variations for comparison. The tests will be
conducted in the ITT Fuse (Technological Institute for
Testing and Functional Safety) of the UNISINOS
(Universidade do Vale do Rio dos Sinos). Each prototype
will perform an operation analysis, visual analysis,
analysis of the electrical resistance and X-ray diffraction
before and after the test. The tests to be performed will be
of thermal cycles, salt spray, thermal shock and vibration.
Canal-Marques et al / DYNA 81 (186), pp. 146-152. August, 2014.
document, Canada, EPS 2006.
4. Conclusion
There is a recent interest in the research of new
technologies for the recycling of printed circuit boards
generated by the growth of the electronics industry, which
constitute an environmental problem when they are disposed
of, a subject which has been extensively studied. In addition,
regulations and laws in Europe have become stricter regarding
specifications of electronic components; therefore, it is
necessary to conduct further studies on the effects of these
rules and laws in other countries.
Given the difficulty of recycling electronic wastes, studies
are focused on the development of techniques which facilitate
the reuse of these products and/or their components. The
methods of fixing and joining of components in the PCBs have
become increasingly popular among researchers, with a
significant increase in studies of lead-free solders. However, it
is necessary to conduct studies related to alternatives to
traditional processes that do not yet have the attention of
researchers and companies, and to take into account the
performance of the final product (LCA), through integrated
approaches in terms of processes, materials and technologies.
The idea of eliminating the use of welding is not new, but
the methods previously proposed (for example, replacement
with conductive adhesive) have not been accepted by the
market, presumably due to operating difficulties or
unreliability. Only a few works exist which propose
alternatives to the traditional procedure.
This initial study is essential to guide new research,
generate alternatives and test them for specific applications.
Currently, ways in which the electronic components are fixed
to printed circuit boards still lack suitable alternatives to
replace them. Therefore, an alternative fixing PCBs was
proposed, and tested and compared with traditional forms. The
first performance test showed positive results with regard to
the operation of the circuit elements. The prototypes were
hand-made and showed reasonable quality. Better quality is
expected in later works, due to prior knowledge of the
construction and operation of the first prototype.
Acknowledgements
The authors wish to acknowledge the financial support of
CAPES (Brazilian Government Agency for Human Resources
Development), CNPq (Brazilian National Council for
Scientific and Technological Development) and the Euro
Brazilian Windows II Project (EBW II).
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152
A. Canal-Marques, is Product Designer from the UNIJUÍ-RS. He is
Specialist in Graphic Expression from PUC-RS. He earned MSc. in
Materials Engineering from Universidade Federal do Rio Grande do Sul
– UFRGS and studies Doctorate in Materials Engineering in the same
University. He carried out part of his Doctorate study in Universitat
Politècnica de Catalunya. Currently, he is professor in Design,
Architecture and Materials Engineering in Universidade do Vale do Rio
dos Sinos – UNISINOS, where he also coordinates the Material and
Product Design course. He is advisor in the Waste Base Council of the
FIERGS.
M. R. Ortega-Vega, is Chemical Eng. by Universidad del Atlántico.
She studies MSc. in Materials Science and Technology in Universidade
Federal do Rio Grande do Sul – UFRGS.
J. M. Cabrera, is currently a Full Professor in the Department of
Materials Science and Metallurgical Engineering of the UPC, is
responsible for the Materials Forming Area in Fundació CTM Centre
Tecnológic, Manresa, Spain. He teaches subjects Technology of
Materials, Materials Selection in Design, Physical Metallurgy and
Nanomaterials and Nanotechnology at the Technical School of
Industrial Engineering of Barcelona.
C. de Fraga-Malfatti is currently professor and researcher of the
Department of Metallurgy in Universidade Federal do Rio Grande do
Sul – UFRGS. She received her Bs. In Metallurgical Engineering and
MSc. in Materials Science and Technology from UFRGS. She earned
Doctorate degree from UFRGS and Université Paul Sabatier, Toulouse
III.